1. Field of the Invention
The present invention relates to an absorbent article.
2. Related Art
Examples of conventional absorbent articles that absorb excreta emanated from the bodies include sanitary napkins, disposable diapers, and training pants. The absorbent articles, which are appropriately used depending on lifestyles, care levels, or the like of wearers, include liquid-permeable surface sheets, liquid-impermeable back sheets, and absorbent bodies arranged between the surface sheets and the back sheets, and are so adapted that the absorbent bodies keep the emanated excreta such as urine through the surface sheets and the back sheets prevent the excreta from leaking out of the absorbent articles at the time of wearing.
Furthermore, disposable diapers of various types such as unfolded types and pants types have been proposed in accordance with the intended uses. The pants-type disposable diaper, for example, is formed in the shape of pants having a trunk opening and a pair of leg openings by previously joining a front trunk-surrounding region and a rear trunk-surrounding region to each other at both their side edges with heat sealing or the like when used. Such pants-type disposable diapers are widely employed by babies to adult incontinent persons.
In the pants-type disposable diaper, it is required that the front trunk-surrounding region and the rear trunk-surrounding region are firmly joined to each other during use and can be easily peeled after use in joint portions at the side edges. However, in recent years, sheet-shaped members having low basis weights may be used from the viewpoint of low cost and reduced environmental load, and sheet-shaped members with specialized stretchability, textures, or the like to improve value of disposable diapers may be used. Such sheet-shaped members reduce the durable strength of joint portions.
Generally, the durable strength of the joint portions has a property of being greatly affected by the basis weights of sheet-shaped members to be joined to each other and the types thereof and their combinations. However, the lower the basis weight of the sheet-shaped members becomes, the lower the durable strength of the joint portions becomes. In order to use sheet-shaped members having a low basis weight, the sheet-shaped members must be, therefore, joined to each other with such a joint pattern that the durable strength of the joint portions can be efficiently increased.
On the other hand, Japanese Unexamined Patent Application, First Publication No. 07-227407 (hereinafter referred to as Patent Document 1), for example, discloses a disposable diaper in which sheet-shaped members are joined to each other by a plurality of transverse adhesive lines and at least one longitudinal adhesive line that are discontinuously arranged in one row or two rows in a longitudinal direction.
In the disposable diaper disclosed in Patent Document 1, a sheet laminate including an absorbent body is folded into front and rear portions, and both their respective right and left side portions are joined to each other along the side edges thereof, to form joint portions. The joint portions are composed of a plurality of transverse adhesive lines and at least one longitudinal adhesive line that are formed by way of heat sealing. The transverse adhesive lines are discontinuously arranged in one row or two rows in a longitudinal direction, and the at least one longitudinal adhesive line is provided so as to come into contact with or intersect at least one of the transverse adhesive lines.
In a case where the at least one longitudinal adhesive line is provided closer to an outer edge of the joint portion, for example, in the disposable diaper disclosed in Patent Document 1, when a load is applied to a joint portion facing a transverse force, perpendicular to the longitudinal direction, to attempt to peel a joint region, the longitudinal adhesive line facing the transverse force is in contact with the transverse adhesive lines. In the disposable diaper disclosed in Patent Document 1, the joint part facing the transverse force is thus dispersed. Therefore, the joining strength cannot be sufficiently increased even if the bonding area is increased.
On the other hand, in a case where the at least one longitudinal adhesive line is provided at an inner end of the joint portion in the disposable diaper, for example, a sufficient strength is exhibited for the transverse force. However, the adhesive line itself functions as an inductive line for cutting in the longitudinal direction of the joint portion. When a force is applied in the longitudinal direction, for example, when a wearer pulls up the disposable diaper at the time of wearing, the joint portion may be torn with little force.